The visual system is among the most accessible and readily studied parts of the nervous system. Understanding it will greatly increase our ability to understand the brain as a whole. The research proposed in this application is aimed at increasing our basic understanding of color vision, in particular, and the organization and development of the nervous system in general. The experiments proposed here will help resolve some of the conflicts evident in presently-accepted theoretical and experimental accounts of color. Studies of the possible existence of asymmetric opponent mechanisms will aid in determining the adequacy of current accounts and, if necessary, in improving them. Both psychophysical studies with human observers and electrophysiological studies from macaque monkey will be coordinated and correlated to increase the power of the results from each alone. Some experiments will examine the existence and characteristics of the color-selective mechanisms that respond to intensity contrast. No full understanding of intensity contrast vision is possible without elucidating the role of these mechanisms. Other studies proposed will examine the processing of visual motion-- one of the most important of the visual abilities--at isoluminance. Color motion vision is remarkably and curiously deficient. To understand this will allow a much greater understanding of the visual processing of motion in general and of the peculiarities associated specifically with the anatomical substrate that is responsible for color vision. Motion vision in the color system will be studied by a variety of psychophysical experiments using isoluminant patterns. These experiments will have counterparts in physiological studies designed to use the same stimuli and similar methods. This will make it possible to develop a much fuller and more thorough understanding of the system.